This invention concerns a gas burner and also a reverberatory furnace provided with at least one gas burner.
Herein a reverberatory furnace means a furnace in which heating flames are directed into a combustion chamber above a tank containing a load to be melted or maintained molten and wherein hot products of combustion circulate above the tank and heat radiates down onto the surface of the tank load from said flames and from surfaces of the chamber.
High temperature, for example 1000.degree. C. and above, melting of metals and non-metal materials can be achieved in a reverberatory furnace by the above surface firing of the process material or load with gas flames. Heat transfer to the process material or load occurs through convection from the hot combustion product flows and from radiant heat transfer either directly from the flame and/or from adjacent furnace surfaces. The thermal efficiency and rate of melting of the process normally depends on the flame radiant heating properties since this heat transfer mechanism is more effective than convection at higher process temperatures (i.e. greater than 1200.degree. C.).
High process temperatures also require high flame temperatures and this is often achieved by using pre-heated combustion air or mixing the fuel gas with oxygen. Both techniques result in increased levels of combustion generated pollutants, in particular NOx. Increasing the radiant emissivity of gas flames would result in greater heat transfer to the process, lower flame temperatures, and hence lower NOx emission levels.
An object of the invention is to provide a gas burner intended to produce flames having greater flame luminosity and emissivity, a higher heat transfer rate and lower NOx emission levels than gas burners (not having the increased luminosity and emissivity) currently available for high temperature processes, for example processes performed at substantially 1000.degree. C. or above.